CN1143523C - Co-channel interference detection network for HDTV receiver - Google Patents
Co-channel interference detection network for HDTV receiver Download PDFInfo
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- CN1143523C CN1143523C CNB988128578A CN98812857A CN1143523C CN 1143523 C CN1143523 C CN 1143523C CN B988128578 A CNB988128578 A CN B988128578A CN 98812857 A CN98812857 A CN 98812857A CN 1143523 C CN1143523 C CN 1143523C
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/02—Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation
- H04L27/06—Demodulator circuits; Receiver circuits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/14—Picture signal circuitry for video frequency region
- H04N5/21—Circuitry for suppressing or minimising disturbance, e.g. moiré or halo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
- H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
- H04N21/438—Interfacing the downstream path of the transmission network originating from a server, e.g. retrieving MPEG packets from an IP network
- H04N21/4382—Demodulation or channel decoding, e.g. QPSK demodulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/04—Synchronising
- H04N5/08—Separation of synchronising signals from picture signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/44—Receiver circuitry for the reception of television signals according to analogue transmission standards
- H04N5/455—Demodulation-circuits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
- H04N21/41—Structure of client; Structure of client peripherals
- H04N21/426—Internal components of the client ; Characteristics thereof
Abstract
A receiver for processing a VSB modulated signal containing terrestrial broadcast high definition television information and a pilot component includes an input analog-to-digital converter (19) for producing a datastream which is oversampled at twice the received symbol rate, and a digital demodulator (22) with a data reduction network in a phase control loop. A segment sync detector (24) uses an abbreviated correlation reference pattern to recover a twice symbol rate sampling clock for the digital converter (19). A DC offset associated with the pilot component is removed (26) from the demodulated signal before it is applied to an NTSC interference detection network (30). The interference detection network (30) includes a comb filter network responsive to a twice symbol rate sampled data datastream, and exhibits a sample delay dimensioned to avoid aliasing in the combed frequency spectrum, thereby increasing the effectiveness of NTSC co-channel interference detection.
Description
Technical field
The present invention relates to a kind of receiver system that is used to handle vestigial sideband modulation type high definition TV (HDTV) signal that proposes such as U.S. Major Leagues.
Background technology
Restore data from the modulation signal that transmits digital information with sign format requires three functions usually in receiver: the timing recovery of sign synchronization, carrier wave recovers (frequency demodulation is to base band), and channel equalization.Timing recovery is one can make receiver clock (time base) and the synchronous processing procedure of transmitter clock by it.This allows received signal to be sampled in the best time, points to the relevant amplitude limit error of (decision-directed) processing to reduce with the judgement of receiving symbol value.It is a processing procedure that carrier wave recovers, and by this processing procedure, the radiofrequency signal of reception is being down-converted to a lower IF passband (for example near base band) back frequency displacement to base band, to allow the recovery of modulating baseband information.Adaptive channel equalizer is a processing procedure, and by this processing procedure, the situation about changing in the signal send channel and the influence of interference are compensated.This processing procedure adopts filter usually, and these filters are eliminated amplitude and the phase distortion that causes owing to the time dependent characteristic of the frequency of transmission channel, thereby improved sign determination ability is provided.
Summary of the invention
According to a first aspect of the invention, provide a kind of being used in to be used for handling the received device that contains the vestigial sideband modulation signal of the high-definition video data of representing by residual sideband symbol cluster and suffer the system of cochannel interference, wherein said data have the data frame format that is made of a continuous data frame, this Frame comprises the field synchronization component as the beginning of a plurality of data segments, and this device comprises:
Respond above-mentioned received signals, in order to produce a device that is flowed by demodulated data;
Be used for being carried out filtering by demodulated data stream to above-mentioned, with produce a filtered demodulation the device of data flow;
Be used to provide the device of reference signal;
Be used for the said reference signal is carried out filtering, to produce the device of a filtered reference signal;
One has the NTSC interference detector that a fan-in network and is connected the output on the signal processing path; And
Be used for above-mentioned by demodulated data stream, said reference signal, above-mentioned filtered demodulation data flow and the above-mentioned filtered reference signal device that offers above-mentioned fan-in network; Wherein
Be added on the above-mentioned fan-in network above-mentioned by demodulated data stream and above-mentioned filtered demodulation data flow, comprise the symbol data that speed that the symbol rate with above-mentioned received signal doubles is taken a sample by mistake.
According to a second aspect of the invention, provide a kind of being used in to be used for handling the received device that contains the vestigial sideband modulation signal of the high-definition video data of representing by residual sideband symbol cluster and suffer the system of cochannel interference, wherein said data have the data frame format that is made of a continuous data frame, this Frame comprises the field synchronization component as the beginning of a plurality of data segments, and this device comprises:
Respond above-mentioned received signal,, it is characterized in that in order to produce a demodulator that is flowed by demodulated data:
Filter, its response is above-mentionedly flowed by demodulated data, be used to decay with tangible NTSC cochannel interfering energy respective frequencies on information, in order to produce a filtered data flow;
The signal quality analyzer, its response is above-mentioned by demodulated data stream and above-mentioned filtered data flow, in order to produce a representative in the above-mentioned control signal that has interference in by demodulated data stream; And
Respond the delivery channel of above-mentioned control signal, be used for when above-mentioned control signal shows that existence is disturbed, above-mentioned filtered demodulated data stream being added to delivery channel, otherwise just be added to above-mentioned delivery channel by demodulated data stream above-mentioned; Wherein:
By above-mentionedly being flowed by demodulated data that above-mentioned demodulator produces, the speed that doubles with the symbol rate of above-mentioned received signals is crossed is taken a sample; And
The sampling that above-mentioned filter presents greater than 12 postpones.
According to a third aspect of the invention we, provide a kind of being used in to be used for handling the received method that contains the vestigial sideband modulation signal of the high-definition video data of representing by residual sideband symbol cluster and suffer the system of cochannel interference, wherein said data have the data frame format that is made of a continuous data frame, this Frame comprises the field synchronization component as the beginning of a plurality of data segments, and this method may further comprise the steps:
Produce one by the demodulated symbols data flow from above-mentioned received signal, its speed that doubles with the symbol rate of above-mentioned received signals is crossed takes a sample;
Postpone to be carried out filtering by demodulated data stream to be higher than 12 sampling, with the information on the frequency of the tangible NTSC cochannel interfering energy of decay representative to above-mentioned;
To above-mentioned filtered demodulation data flow analyze, have the control signal disturbed above-mentioned in by demodulated data stream in order to produce a representative; And
One delivery channel is provided, is used for above-mentioned filtered demodulated data stream is added to delivery channel when above-mentioned control signal shows to exist when disturbing, otherwise just is added on the above-mentioned delivery channel by demodulated data stream above-mentioned.
Description of drawings
Fig. 1 comprises the block diagram of the part of the high-definition TV receiver of device in accordance with the principles of the present invention.
Fig. 2 describes the data frame format that is used for according to the VSB modulation signal of HDTV system of U.S. Major Leagues.
The detailed structure of the digital demodulator/carrier recovery network in Fig. 3 presentation graphs 1.
The section synchronizing indicator in Fig. 4 presentation graphs 1 and the detailed structure of symbol clock recovery network.
Fig. 5 has described the signal waveform that helps to understand network operation shown in Figure 4.
Fig. 6 represents a kind of detailed structure of compensating network, and this network is used for eliminating the direct current biasing by the symbol data streams of the system handles of Fig. 1.
The detailed structure of NTSC co-channel interference detection network in the system of Fig. 7 presentation graphs 1.
Fig. 8 represents and the relevant frequency spectrum of network operation among Fig. 7.
Embodiment
In Fig. 1, the HDTV signal of terrestrial broadcasting analog input is by the fan-in network 14 that comprises rf tuning circuit and comprise that the IF processor 16 of two frequency conversion tuning devices of being used to produce intermediate frequency (IF) passband output signal and suitable automatic gain control (AGC) circuit handles.The signal that receives is to propose and the 8-VSB modulation signal of the carrier suppressed used in the U.S. as Major Leagues.This VSB signal is by one-dimensional data symbol cluster (constellation) expression, and wherein having only an axle to comprise will be by the quantized data of receiver recovery.For simplify this figure, do not illustrate be used to shown in the signal of functional block timing.
As described in the HDTV of the Major Leagues system specifications that came into force on April 14th, 1994, the VSB transmission system transmits the data with specified data frame format shown in Figure 2.The little pilot signal that is in the inhibition carrier frequency is added to transmission signals and is beneficial to realize carrier lock on vsb receiver.Referring to Fig. 2, each Frame comprises two fields, and wherein each comprises 313 sections of 832 multistage symbols.Each first section is called field synchronization segments, and 312 remaining sections are called data segment.Data segment generally includes the packet that meets MPEG.Each data segment comprises the section synchronization character of four symbols, then is 828 data symbols.The section of each comprises the section synchronization character of four symbols, then be the field synchronization component of the PN sequence of pseudo random number (PN) sequence that comprises 511 predetermined symbols and three 63 predetermined symbols, wherein one of the centre of the PN sequence of three 63 predetermined symbols is anti-phase in continuous field.VSB mode control signal (size of definition VSB symbol conformation) is the sequence of last 63PN then, is the symbol of 96 preservations and 12 symbols that duplicate from front surface field subsequently.
Continuation was converted to the numeric character data stream of sampling referring to Fig. 1 by analog to digital converter (ADC) 19 from the passband IF output signal of unit 16.The output of ADC19 sampling digital data stream, be demodulated to base band by all-digital demodulation device/carrier recovery network 22.This is to be undertaken by the little reference pilot carrier in the VSB data flow of response reception by all-digital phase-locked loop.Unit 22 produces will export I-phase demodulating symbol data streams in greater detail with reference to Fig. 3.
ADC19 comes over-sampling to import the VSB symbol data streams of 10.76 million symbol/seconds by the sampling clock that use doubles the 21.52MHz of receiving symbol rate, thereby the 21.52 million samples/sec data flow of crossing sampling of two sampling values of each symbol are provided.Use two sample values of this each symbol based on the processing of sample but not the processing based on symbol of symbol (sample value of each symbol) one by one can produce the favourable operation with follow-up signal processing capacity relevant with all DC compensation as will be discussed unit 26 and NTSC interference detector 30.
Synchronous and the symbol clock recovery network 24 of the section of being that is associated with ADC19 and demodulator 22.Network 24 detects and the repeating data section synchronized component of each Frame is separated with random data.Section be used to synchronously the to regenerate clock of 21.52MHz of correct phasing, it is used for by analog to digital converter 19 control datas stream symbol sampler.As what discuss in conjunction with Figure 4 and 5, network 24 helps using two symbol dependency basis quasi-modes of abbreviation to come detection segment synchronous with two relevant symbol data correlators.
As what will discuss with reference to figure 6, DC compensation unit 26 uses the adaptive tracing circuit, and the direct current biasing component that causes because of the pilot signal component is eliminated from the VSB signal of demodulation.Unit 28 detects the data fields synchronized component by the data segment of each reception is compared with the ideal field reference signal in the memory that is stored in receiver.Except field synchronization, field sync signal also is provided for the training signal of channel equalizer 34.
NTSC (National Television System Committee) Interference Detection and inhibition are carried out unit 30 discussed in detail by reference Fig. 7 and 8.Afterwards, this signal is by channel equalizer 34 adaptive equalizations of operating with the compound mode of blindness (blind), training (training) and judgement directing mode.Equalizer 34 can be the type described in the article " the VSB modulation subsystem design that Major Leagues' digital television receiver is used " of people such as W.Bretl among the HDTV of Major Leagues system specifications and the August nineteen ninety-five IEEETransactions on Consumer Electronics.Equalizer 34 also can be the type of people such as Shiue description in the common unsettled U.S. Patent Application Serial Number 09/102,885 that proposed on June 23rd, 1998.The output stream of detector 30 down-converted to the sampling value/symbol data flow of (10.76 million symbol/second) before equalizer 34.This down-conversion can be realized by suitable following sampling microwave network (not shown in order to simplify accompanying drawing).
Demodulation in the unit 22 is controlled (APC) ring by digital automatic phase and is carried out to realize that carrier wave recovers.Phase-locked loop uses weight of pilot frequency as the reference of initial acquisition and use common phase detectors in the phase place collection.Pilot signal embeds in the data flow that receives, and it comprises the data that present at random, are similar to the pattern of noise.Random data is not considered by the filtering operation of demodulator APC loop basically.The input signal of 10.76 million symbol/seconds of ADC19 is the signal that approaches base band, and the center of its VSB frequency spectrum is at 5.38MHz, and weight of pilot frequency is positioned at 2.69MHz.At 21.52MHz, input traffic is beneficial to by the ADC19 twice and crosses sampling.In the demodulated data stream from unit 22, weight of pilot frequency is arrived DC to downshift.
Fig. 3 represents the detailed structure of digital demodulator 22.From the 8-VSB modulation that comprises the very low frequency weight of pilot frequency of ADC19 and the data symbol data flow of over-sampling, be applied in the input of hilbert filter 320 and delay cell 322.Filter 320 is divided into " I " (homophase) and " Q " (90 ° of phase differences) component to the IF sampled data stream of input.Postpone 322 and present the delay of mating with hilbert filter 320.I and Q component are by using complex product musical instruments used in a Buddhist or Taoist mass 324 to rotate to base band in the APC ring.In case this loop is by synchronously, then the output of multiplier 324 is compound baseband signals.Data flow from the output I of multiplier 324 is used as actual demodulator output, and also is used for by using low pass filter 326 to obtain the weight of pilot frequency that is received data flow.The phase place that is used to obtain received signals from the data flow of multiplier 324 output Q.
In phase control loop, be applied to respectively on low pass filter 326 and 328 from the I and the Q output signal of multiplier 324. Filter 326 and 328 is Nyquist low pass filters that cut-off frequency is about 1MHz, and is used for reducing before being taken a sample under the data at 8: 1 by unit 330 and 332 execution the bandwidth of signal.The Q signal of following sampling is by 336 filtering of automatic frequency control (AFC) filter.After filtering, Q signal by unit 338 amplitude limits to reduce the dynamic range requirement of phase detectors 340.Phase detectors 340 detect and proofread and correct and are applied to the I of its input and the phase difference between the Q signal, and produce by the output phase difference signal such as APC filter 344 filtering of second level low pass filter.The phase difference that unit 340 detects represent to expect near the difference on the frequency between the pilot signal frequency of the pilot signal frequency of direct current and reception.
If the pilot signal that receives is rendered as the frequency near direct current of expectation, then AFC unit 336 does not produce phase shift.Be input to the I of phase detectors 340 and the weight of pilot frequency of Q channel, will not depart from the phase relations of 90 degree each other mutually, thereby phase detectors 340 produce null values or near the phase error input signal of null value.Yet if the pilot signal that receives is rendered as wrong frequency, AFC unit 336 will produce phase shift.This will cause phase difference additional between the I of the input that is applied to phase detectors 340 and the Q channel pilot frequency signal.Detector 340 produces an output error value in response to this phase difference.
From the filtered phase error signal of filter 344 by taking a sample 1: 8 on the interpolater 346 with computing unit 330 and the 332 previous following samplings of carrying out, so that NCO 348 is operated in 21.52MHz.The output of interpolater 346 is applied to the control input of NCO 348, and its local regeneration is used for the pilot signal that demodulation is received data flow.NCO 348 comprises and being used for by response from the phase control signal of unit 340,344 and 346 and at the sine and the cosine check table of phase calibration regeneration pilot tone.The output Be Controlled of NCO 348, the phase error signal that makes detector 340 produce up to the I of multiplier 324 and Q signal output is actually till zero, thus the baseband I signal that indicates suitable demodulation is present in the output of multiplier 324.
In digital demodulator 22, in fact main signal processor comprises element 336,338,340 and 344.8: 1 times samplings that provided by unit 330 and 332 help saving the processing power and the hardware of demodulator, and, promptly use the clock timing of the clock of 21.52MHz/8 or 2.69MHz rather than 21.52MHz and allow highly-efficient treatment by making APC loop element 336,338,340 and 344 a lower clock frequency timing.When digital signal processor (DSP) is used to implement network 22 particularly the phase-detection ring time, for example by requiring command code line still less pari passu, the result of described data conversion has improved software efficiency.The circulation of DSP can be used as other signal processing purpose.When special-purpose integrating circuit (ASIC) was used to implement network 22, the result of data conversion had reduced the requirement of hardware and power and has reduced the surf zone of integrating circuit.Demodulator utilizes weight of pilot frequency to realize that carrier wave recovers more favourable, and adopts the feedback processing of feed-forward process rather than use amplitude limiter decision data more complicated and consuming time.
The I channel data stream of demodulation is applied in the section that is shown specifically to Fig. 4 and Fig. 5 synchronously and symbol clock recovery unit 24.When repeating data section lock-out pulse was recovered by the random data pattern that is received data flow, section was used to the sampling clock of the 21.52MHz that doubles symbol rate of the suitable phasing used by regeneration control analog to digital converter 19 (Fig. 1) sampling operation synchronously and realizes that suitable symbol regularly.Fig. 5 has described ground station's signal of modulating for the 8-VSB according to the HDTV of Major Leagues standard and has had eight grades of synchronous (7 to+7) data segments of dependent segment.Section occurs in the beginning of each data segment synchronously and takies four mark spaces.Section is synchronously by pattern 1 ,-1 ,-1,1 definition corresponding to from+5 to-5 section lock-out pulse width of cloth level.
Synchronously per 832 symbols of four sign fields occur once, but since data have at random and be similar to the characteristic of noise, so be difficult to be arranged in the VSB digital data stream of demodulation.Synchronous for detection segment under this condition, normally the I channel data stream of demodulation is applied to an input of data correlator, and having 1,-1, the reference mode of-1,1 characteristic is applied to the reference input of this correlator, to compare with demodulating data.Correlator produces consistent with the reference mode reinforcement of per 832 characters.The data event of strengthening is by the accumulator accumulation relevant with this correlator.(not strengthening) at random of inserting relevantly then disappears with respect to the dependent segment synchronized component of strengthening.The network that is used for the section of recovery synchrodata of this mode for example can be known from people's such as the previously mentioned HDTV of Major Leagues standard and Bretl article.
Here as can be seen, although section generally is difficult to the location synchronously, it is difficult to detect when multipath (" ghost image ") exists especially.And, this shows that the latter two characteristics of segment synchronization pattern (amplitude rank) (1,1) is destroyed (corrupt) by the transmission distortion such as multipath easily, but preceding two characteristics (1 ,-1) of segment synchronization pattern are difficult to especially but destroy.Can judge that in addition even preceding two amplitude responses (1 ,-1) of segment synchronization pattern are destroyed, they generally also are to destroy in an identical manner, this just makes preceding two characteristics detect more easily by correlation technique.Thereby in disclosed system, be added to and be used for detection segment synchronization basic standard pattern on the correlator, preferably constitute by preceding two pattern levels (1 ,-1) rather than by all four pattern levels (1 ,-1 ,-1,1).Like this, the reference mode of correlator preferably includes only two mark spaces.
In Fig. 4, be added to a signal input part and 832 symbol correlator 420 of phase detectors 410 from the over-sampling output stream of demodulator 22 (Fig. 1 and 3).Another signal input part of phase detectors 410 is from the relevant dependency basis quasi-mode generator 430 that comprises correlator 420, connect with the benchmark input end of correlator 420 and the data correlation process path receiving inputted signal of section integrator and accumulator 424.It is synchronous that in fact correlator 420 responds symbol coded data section.Reference mode generator 430 provides the reference mode 1 ,-1 of simple abbreviation, thereby can allow to use better simply correlator network.This better simply reference mode is in synchronous detecting is handled, and particularly (confusion) obscured in unlikely generation under the condition of poor signal, and this is because used more reliable and more stable information.If four two destructions in relevant, disclosed system is also unlikely to be confused.In addition, significantly reduce the computing time of correlator 420.
The output of correlator 420 is by unit 424 integrations and accumulation.The section synchronizing generator 428 that comprises the comparator with predetermined threshold is by producing the section output of response unit 424 synchronously in reasonable time at interval corresponding to data segment sync in data flow.This situation takes place when surpassing predetermined level in the accumulation (section is external behavior synchronously) of the data event of strengthening.The synchronous phase place of the section that phase detectors 410 produce unit 428 compares with a section synchronous phase place that manifests in the demodulated data stream from unit 22, and produces the output phase error signal.This error signal is carried out low-pass filtering by automatic phase control (APC) filter 434, is applicable to generation to be controlled to be the signal that ACD19 provides the 21.52MHz VCXO (VCXO) 436 that 21.52MHz crosses sampling clock.This sampling clock presents suitable timing when phase error signal is substantially zero by the APC effect.Symbol regularly (clock) recovers to finish in this point.The section that unit 428 produces also is applied to other decoder circuit that comprises automatic gain control (AGC) circuit (not shown) synchronously.
Because the weight of pilot frequency of the VSB signal medium and low frequency suppressed carrier that receives, so in demodulation output I symbol data, there is a direct current biasing from demodulator 22.This direct current biasing is relevant with each symbol and eliminated by compensating network 26 (Fig. 1) before further handling.I.e. ± 7 ± 5 ± 3 ± 1 the recovery of symmetrical symbols value of 8-VSB signal is convenient in the elimination that is transmitted the DC component of symbol.Figure 6 shows that the detailed structure of network 26, it is actually a direct current tracking feedback network.The device of the network 26 among Fig. 6 helps coming timing to double character rate, thereby eliminates DC component fast.This operation has promoted the quick convergence of receiver and its several independent particle systems, is used to be treated to the suitable operating condition of the received video data that shows usefulness with rapid generation.
In Fig. 6, comprise the input that the sampling demodulated data stream is added to subtractive combination device (subtractive combiner) 610 of crossing of useless direct current biasing.A reverse input end (-) of combiner 610, the control signal that produces by following output and receive the DC compensation voltages from DC voltage generator 616 according to combiner 610.Decay gradually with the sample rate that doubles character rate by feedback operation from the direct current biasing in the output signal of combiner 610.This direct current biasing is detected by unit 622 and by comparator 624 it is compared with a benchmark.The output of comparator 624 indicates the amplitude and the polarity of remaining direct current biasing, and is used for producing control signal by control-signals generator 626.Then, this control signal makes the amplitude and the polarity of the D. C. value of generator 616 incremental and demodulated data stream combination.This processing procedure is proceeded, until reach a kind of the stable state that D. C. value regulates no longer is provided by feedback operation unit 616 till.Generator 616 can provide the positive and negative DC offset value, and this can make that because of transmission-channel interference adding (just) direct current biasing on transmitter changes, and not only needs positive offset but also need negative offset like this on receiver.
Fig. 7 represents the detailed structure of NTSC co-channel interference detection network 30 shown in Figure 1.As what explained in the HDTV of the Major Leagues system specifications, the interference rejection of VSB transmission system is based on the frequency location of the solvent of the NTSC co-channel interference signal within the 6MHz television channel, and the periodicity trap of the base band comb filter of vsb receiver.These comb filter traps present high decay (zero) at the frequency location that disturbs high energy NTSC component.These components comprise the video carrier that is positioned at 1.25MHz from low wavestrip edge, are higher than the colour subcarrier that is positioned at 3.58MHz of video carrier frequency, and the sound carrier that is positioned at 4.5MHz on the video carrier frequency.
NTSC disturbs and is detected by circuit shown in Figure 7, and wherein signal-the interference plus noise of field synchronization pattern is measured at the input and output side of comb filter network, and these patterns are compared to each other.The reference field synchronous mode of Cai Yonging is programming and " ideal " version of the VSB signal field synchronous mode of reception that be local storage for this reason.
In Fig. 7, the I channel symbol data of over-sampling demodulation are added to NTSC and suppress an input of comb filter 710, the first input end of multiplexer 745, and an input of subtractive combination device 720.Comb filter 710 comprises a subtracter 712, and it deducts the sampling value that delay element 714 postpones from input I data, to produce the I channel symbol data flow of a pectination.The high energy that comb filter 710 is mentioned in front disturbs and produces significant amplitude fading or " zero " on the NTSC frequency.Be added to second input of multiplexer 745 from the pectination I data of filter 710.The delay element 714 of comb filter helps showing subsequently the 24-sampling of describing is postponed.
Programming 21.52 million sampling/second (doubling symbol rate) reference field synchronous mode, obtain from local storage in field synchronization interim of receiving data stream.The field synchronization reference mode is added to an input of NTSC band resistance comb filter 718, and the reverse input end (-) of combiner 720.Comb filter 718 is similar with comb filter 710, and also includes to be beneficial to and show the delay element that the 24-sampling postpones.Network among Fig. 7, particularly comb filter 710,718 and relevant delay network, clock is under the frequency of 21.52MHz.
In first error signal that the output of combiner 720 produces, be illustrated in poor between received field synchronous mode in the input traffic and the reference field synchronous mode.This error signal is by 722 squares of unit and by unit 724 integrations.In second error signal that the output of combiner 730 produces, be illustrated in poor between received field synchronous mode after filter 710 comb filterings and the reference field synchronous mode after filter 718 comb filterings.This second error signal is by 732 squares of unit and by unit 734 integrations.The energy of error signal is separately represented in unit 722 and 732 output.Integrator 724 and 734 integral output signal are represented the not signal-interference plus noise amount of the received field synchronized component of comb filtering and comb filtering respectively.The signal of the representative energy of these integrations is added to the respective input of energy detector (comparator) 740 of the first and second error signal sizes of comparison integration.The output signal of detector 740 is added to the control input end of multiplexer 745, and one of input signal that makes it to be used to multiplexer 745 is provided as " data output " presents higher quality, and promptly having preferably, noise adds interference ratio.Thereby under the situation that significant NTSC cochannel disturbs, the comb filtering output signal of filter 710 will be from multiplexer 745 outputs, and unfiltered receiving symbol data flow will be exported when this interference is non-existent simultaneously.
The take a sample use of I channel data and field synchronization reference mode data of the mistake that postpones to use with 24-sampling in comb filter 710 and 718 helps producing whole spectrum informations that relevant NTSC cochannel disturbs.This is beneficial to the more accurate NTSC interference analysis of generation and detection and comb filtering preferably.Particularly, 24 samplings in crossing the comb filter 710 and 718 that sampling input data and related circuit timing use postpone to produce the frequency spectrum of comb filtering, and this frequency spectrum is not provided input traffic and destroys by the phase place and the amplitude aliasing effects of operating comb filter 710 and 718 generations with the symbol rate of 10.76 million symbol/seconds by the symbol rate with 10.76 million symbol/seconds.Shown in Figure 8 at the final frequency spectrum that the output of comb filter 710 and 718 produces, and comprise two near the 10.76MHz center but divide the full NTSC passband component of the comb filtering of opening with 10.76MHz.The decay trap disturbs the NTSC frequency to occur at described high energy.
Fig. 7 shows a kind of form of the NTSC co-channel interference detector that comprises element 722,724,732,734 and 740.But also can use the detector of other type.Thereby these elements can with four the input detectors be that so-called black box is represented, wherein this detector can be programmed with the requirement according to particular system and operate.In this case, four inputs are that two cross take a sample (two sampling value/symbols) that are connected with combiner 720 are imported, and two inputs of sampling excessively that link to each other with combiner 730, wherein the output particular importances of the filter 710 that is connected with the input of combiner 730.
As shown in Figure 8, the device of Fig. 7 can produce frequency spectrum clearly, and not owing to the relevant amplitude that causes than the last band edge of lower passband component and the frequency overlap of the following band edge of upper-passband component and the destruction (aliasing) of phase place.Therefore, the cochannel Interference Detection of element 720,722,724,730,732,734 and 740 execution are more accurate with the detection of system's execution of the comb filter with 12-sampling delay of the symbol rate processing input data of 10.76 million symbol/seconds than employing.Under latter event, amplitude and phase place are destroyed and may be produced near 5.38MHz, and wherein the passband component is overlapping up and down, and this moment, the passband component can not fine coupling and can not cancel this overlapping.This bad coupling may take place comprising under the situation of the signaling channel of multipath for example.The situation of this aliasing has reduced the effect of NTSC cochannel Interference Detection, and is avoided by system of the present disclosure.
Claims (13)
1. one kind is used in to be used for handling and receivedly contains by the vestigial sideband modulation signal of the high-definition video data of residual sideband symbol cluster representative and the device that suffers the system that cochannel disturbs, wherein said data have the data frame format that is made of a continuous data frame, this Frame comprises the field synchronization component as the beginning of a plurality of data segments, and this device comprises:
Respond above-mentioned received signals, in order to produce a device that is flowed by demodulated data;
Be used for being carried out filtering by demodulated data stream to above-mentioned, with produce a filtered demodulation the device of data flow;
Be used to provide the device of reference signal;
Be used for the said reference signal is carried out filtering, to produce the device of a filtered reference signal;
One has the National Television System Committee interference detector that a fan-in network and is connected the output on the signal processing path; And
Be used for above-mentioned by demodulated data stream, said reference signal, above-mentioned filtered demodulation data flow and the above-mentioned filtered reference signal device that offers above-mentioned fan-in network; Wherein
Be added on the above-mentioned fan-in network above-mentioned by demodulated data stream and above-mentioned filtered demodulation data flow, comprise the symbol data that speed that the symbol rate with above-mentioned received signal doubles is taken a sample by mistake.
2. according to the device of claim 1, it is characterized in that said reference signal and above-mentioned filtered reference signal comprise with the speed of the above-mentioned multiple of the symbol rate of above-mentioned received signals and crossed the symbol data of taking a sample.
3. according to the device of claim 1, it is characterized in that:
The above-mentioned device that is used for filtering comprises a comb filter network; And
Above-mentioned fan-in network comprises that a response is above-mentioned and asked poor network by first of demodulated data stream and said reference signal, and one respond above-mentioned filtered demodulation data flow and above-mentioned filtered reference signal second ask poor network.
4. according to the device of claim 1, it is characterized in that described reference signal is a field synchronization reference mode.
5. one kind is used in to be used for handling and receivedly contains by the vestigial sideband modulation signal of the high-definition video data of residual sideband symbol cluster representative and the device that suffers the system that cochannel disturbs, wherein said data have the data frame format that is made of a continuous data frame, this Frame comprises the field synchronization component as the beginning of a plurality of data segments, and this device comprises:
Respond above-mentioned received signal,, it is characterized in that in order to produce a demodulator that is flowed by demodulated data:
Filter, its response is above-mentionedly flowed by demodulated data, be used to decay with tangible National Television System Committee cochannel interfering energy respective frequencies on information, in order to produce a filtered data flow;
The signal quality analyzer, its response is above-mentioned by demodulated data stream and above-mentioned filtered data flow, in order to produce a representative in the above-mentioned control signal that has interference in by demodulated data stream; And
Respond the delivery channel of above-mentioned control signal, be used for when above-mentioned control signal shows that existence is disturbed, above-mentioned filtered demodulated data stream being added to delivery channel, otherwise just be added to above-mentioned delivery channel by demodulated data stream above-mentioned; Wherein:
By above-mentionedly being flowed by demodulated data that above-mentioned demodulator produces, the speed that doubles with the symbol rate of above-mentioned received signals is crossed is taken a sample; And
The sampling that above-mentioned filter presents greater than 12 postpones.
6. according to the device of claim 5, it is characterized in that:
Above-mentioned by the demodulated symbols data flow, crossed with the speed of 2 times of the symbol rates of above-mentioned received signals and to be taken a sample; And
Above-mentioned filter presents one 24 samplings at least and postpones.
7. according to the device of claim 5, it is characterized in that the output spectrum that above-mentioned filter generation one is made of underlapped last passband and following passband.
8. according to the device of claim 5, it is characterized in that above-mentioned filter is a comb filtering device, this comb filtering device comprises: a response above-mentioned by demodulated data stream filtered demodulation is provided first comb filter of data flow; And described device comprises that also response one reference signal provides second comb filter of filtered reference signal;
And above-mentioned analyzer comprises:
Be used for determining above-mentioned by first detector of the difference of demodulated data stream and said reference signal;
Be used for determining above-mentioned filtered demodulation data flow and second detector of the difference of above-mentioned filtered reference signal; And
The output that is used for more above-mentioned first and second detector is to produce the device of above-mentioned control signal.
9. device according to Claim 8 is characterized in that the said reference signal is a field synchronization reference mode.
10. one kind is used in and is used for handling the received method that contains by the vestigial sideband modulation signal of the high-definition video data of residual sideband symbol cluster representative and suffer the system that cochannel disturbs, wherein said data have the data frame format that is made of a continuous data frame, this Frame comprises the field synchronization component as the beginning of a plurality of data segments, and this method may further comprise the steps:
Produce one by the demodulated symbols data flow from above-mentioned received signal, its speed that doubles with the symbol rate of above-mentioned received signals is crossed takes a sample;
Postpone to be carried out filtering by demodulated data stream to be higher than 12 sampling, with the information on the frequency of the tangible National Television System Committee cochannel interfering energy of decay representative to above-mentioned;
To above-mentioned filtered demodulation data flow analyze, have the control signal disturbed above-mentioned in by demodulated data stream in order to produce a representative; And
One delivery channel is provided, is used for above-mentioned filtered demodulated data stream is added to delivery channel when above-mentioned control signal shows to exist when disturbing, otherwise just is added on the above-mentioned delivery channel by demodulated data stream above-mentioned.
11. the method according to claim 10 is characterized in that:
By the above-mentioned sampled data stream of crossing that above-mentioned generation step provides, be to cross sampling with the sampling factor 2 that 2 sub-samplings are provided for each symbol; And
Above-mentioned filter step presents 24 samplings and postpones.
12. the method according to claim 11 is characterized in that, above-mentioned filter step produces a frequency spectrum, and its underlapped last passband and following passband by the frequency place of the symbol rate of the above-mentioned received signals of correspondence constitutes.
13. the method according to claim 12 is characterized in that:
Above-mentioned received signal is the data flow of a 8-vestigial sideband modulation; And
The above-mentioned symbol rate of above-mentioned received signals is about 10.76M symbol/second.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9723052.8 | 1997-10-31 | ||
| GBGB9723052.8A GB9723052D0 (en) | 1997-10-31 | 1997-10-31 | High definition television vsb receiver |
| US09/140,143 US6697098B1 (en) | 1998-08-26 | 1998-08-26 | Co-channel interference detection network for an HDTV receiver |
| US09/140,143 | 1998-08-26 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1285993A CN1285993A (en) | 2001-02-28 |
| CN1143523C true CN1143523C (en) | 2004-03-24 |
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ID=26312528
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB988128578A Expired - Fee Related CN1143523C (en) | 1997-10-31 | 1998-10-15 | Co-channel interference detection network for HDTV receiver |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JP2001522203A (en) |
| KR (1) | KR100564836B1 (en) |
| CN (1) | CN1143523C (en) |
| AU (1) | AU1270699A (en) |
| HK (1) | HK1035288A1 (en) |
| WO (1) | WO1999023816A1 (en) |
Families Citing this family (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6707861B1 (en) | 1999-10-26 | 2004-03-16 | Thomson Licensing S.A. | Demodulator for an HDTV receiver |
| KR100392449B1 (en) * | 2001-07-16 | 2003-07-23 | 삼성전자주식회사 | restoring system of digital TV signal and restoration method thereof |
| US7038733B2 (en) | 2002-01-30 | 2006-05-02 | Ericsson Inc. | Television receivers and methods for processing signal sample streams synchronously with line/frame patterns |
| KR100859868B1 (en) * | 2002-05-30 | 2008-09-24 | 삼성전자주식회사 | Carrier Recovery Apparatus of digital broadcasting receiver using the 2 pilot signal |
| WO2004049704A1 (en) * | 2002-11-26 | 2004-06-10 | Thomson Licensing S.A. | An ntsc signal detector |
| AU2003291466A1 (en) * | 2002-11-26 | 2004-06-18 | Thomson Licensing S.A. | Apparatus and method for detecting ntsc co-channel interference |
| JP4392839B2 (en) * | 2002-11-26 | 2010-01-06 | トムソン ライセンシング | Carrier tracking loop lock detector |
| US7672285B2 (en) * | 2004-06-28 | 2010-03-02 | Dtvg Licensing, Inc. | Method and apparatus for minimizing co-channel interference by scrambling |
| KR100577703B1 (en) * | 2004-08-27 | 2006-05-10 | 삼성전자주식회사 | Carrier recovery apparatus for vsb type receiver and methods thereof |
| DE102004054893A1 (en) * | 2004-11-12 | 2006-05-24 | Micronas Gmbh | Method and circuit arrangement for channel filtering analog or digitally modulated TV signals |
| CN1988435B (en) * | 2006-12-19 | 2011-06-08 | 上海广电（集团）有限公司中央研究院 | Digital bit synchronizing method |
| CN101841503B (en) * | 2009-03-20 | 2014-01-15 | 高通创锐讯企业管理(上海)有限公司 | Method for recovering sampling clock in VSB (Vestigial Sideband) modulating system |
| JP5561093B2 (en) * | 2010-10-15 | 2014-07-30 | 富士通株式会社 | Data determination circuit and receiving apparatus |
| CN103297363B (en) * | 2012-02-27 | 2016-03-16 | 晨星软件研发(深圳)有限公司 | Symbol rate checkout gear and symbol rate detection method |
| TWI822030B (en) * | 2022-05-05 | 2023-11-11 | 律芯科技股份有限公司 | Noise shaping digital automatic gain control system |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5087975A (en) * | 1990-11-09 | 1992-02-11 | Zenith Electronics Corporation | VSB HDTV transmission system with reduced NTSC co-channel interference |
| US5260793A (en) * | 1991-07-18 | 1993-11-09 | Zenith Electronics Corporation | Receiver post coder selection circuit |
| US5452015A (en) * | 1994-02-10 | 1995-09-19 | Philips Electronics North America Corporation | Method and apparatus for combating co-channel NTSC interference for digital TV transmission |
| KR960020485A (en) * | 1994-11-14 | 1996-06-17 | 이헌조 | HTV receiver |
| US5546132A (en) * | 1994-12-07 | 1996-08-13 | Goldstar Co., Ltd. | NTSC interference detector |
| KR0151529B1 (en) * | 1995-10-31 | 1998-10-15 | 김광호 | Apparatus and method for controlling the operation selection of ntsc rejection filter |
-
1998
- 1998-10-15 KR KR1020007004456A patent/KR100564836B1/en not_active IP Right Cessation
- 1998-10-15 CN CNB988128578A patent/CN1143523C/en not_active Expired - Fee Related
- 1998-10-15 WO PCT/US1998/021799 patent/WO1999023816A1/en active IP Right Grant
- 1998-10-15 JP JP2000519549A patent/JP2001522203A/en active Pending
- 1998-10-15 AU AU12706/99A patent/AU1270699A/en not_active Abandoned
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Also Published As
| Publication number | Publication date |
|---|---|
| KR20010031426A (en) | 2001-04-16 |
| KR100564836B1 (en) | 2006-03-30 |
| WO1999023816A1 (en) | 1999-05-14 |
| JP2001522203A (en) | 2001-11-13 |
| CN1285993A (en) | 2001-02-28 |
| HK1035288A1 (en) | 2001-11-16 |
| AU1270699A (en) | 1999-05-24 |
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